Variable-length segment copy for compressing index map of palette coding in screen content coding

Abstract

With the emerging applications, such as screen mirroring, and remote play, screen contents coding (SCC) plays important role in video coding recently. Since the characteristics of screen contents are different from nature contents, palette coding is adopted in the current draft standard of HEVC-SCC. The basic idea of the palette coding is to represent the colors of a coding unit (CU) by the indices of selected representative colors. This paper presents that the produced index maps exhibit considerably high spatial correlation. To utilize the spatial correlation among indices, a general 2-D search method is proposed firstly for index map compression. To reduce the memory access and implementation complexity, three simplified search schemes are proposed to balance the coding performance and complexity. The experimental results show that the three simplified methods can achieve 0.6%, 0.5% and 0.9% BD-rate saving respectively, as compared to HM-13.0 + RExt-6.0 test model.